Circuit arrangement for firing a controlled semiconductor valve, particularly a thyristor

Abstract

The invention concerns a circuit arrangement for firing a controlled semiconductor valve, particularly a thyristor, the control path of which is connected to a d-c voltage source by way of the collector-emitter path of a transistor. In order to obtain a control electrode current at the semiconductor valve, which is independent of the d-c voltage of the d-c voltage source and the control electrode characteristic of the semiconductor valve, provision is made, according to the invention, that a resistor is arranged in series with the collector-emitter path of the transistor, and that a Zener diode is connected between the base of the transistor and that terminal of the resistor which is facing away from the transistor.

What is claimed is: 
     
       1. A circuit for controlling the firing of an electric valve comprising: a. a d.c. voltage source, the negative terminal of which is connected to the cathode of said electric valve;   b. an impedance circuit comprising a first resistor in series with a second resistor and a capacitor coupled in parallel across said second resistor;   c. a transistor having its collector emitter path connected in series with said impedance circuit between the positive terminal of said d.c. voltage source and the control electrode of said electric valve; and   d. a zener diode connected between the base of said transistor and the terminal point of said impedance circuit which faces away from said transistor.   
     
     
       2. The circuit of claim 1 and further including a diode poled in the direction of said control electrode in series with said capacitor across said second resistor and a third resistor in parallel with said capacitor. 
     
     
       3. The circuit of claim 2 wherein the ratio of resistance of said second resistor to said first resistor is about 3:1. 
     
     
       4. The circuit of claim 2 wherein the ratio of resistance of said third resistor to said second resistor is about 10:1. 
     
     
       5. The circuit of claim 4 wherein the ratio of resistance of said second resistor to said first resistor is about 3:1. 
     
     
       6. The circuit of claim 1 wherein the ratio of resistance of said second resistor to said first resistor is about 3:1. 
     
     
       7. The circuit of claim 1 wherein the electric valve is a thyristor.